The present invention generally relates to communication systems, and in particular to a system and method for saving power in a mobile communication device.
The use of cellular communication systems having mobile devices which communicate with a hardwired network, such as a local area network (LAN) or a wide area network (WAN), has become widespread. Retail stores and warehouse, for example, may user cellular communications systems with mobile data terminals to track inventory and replenish stock. The transportation industry may use such systems at large outdoor storage facilities to keep an accurate account of incoming and outgoing shipments. In manufacturing facilities, such systems are useful for tracking parts, completed products and defects. Such systems are also utilized for cellular telephone communications to allow users with wireless telephones to roam across large geographical regions while retaining telephonic access. Paging networks also may utilize cellular communications systems which enable a user carrying a pocket sized pager to be paged anywhere within a geographic region.
A typical cellular communications system includes a number of fixed access points (also known as base stations) interconnected by a cable medium often referred to as a system backbone. Also included in many cellular communications systems are intermediate access points which are not directly connected to the system backbone but other wise perform many of the same functions as the fixed access points. Intermediate access points, often referred to as wireless access points or base stations, increase the area within which access points connected to the system backbone can communicate with mobile devices.
Associated with each access point is a geographic cell. The cell is a geographic area in which an access point has sufficient signal strength to transmit data and receive data from a mobile device such as a data terminal or telephone with an acceptable error rate. Typically, access points will be positioned along the backbones such that the combined cell area coverage from each access point provides full coverage of a building or site.
Mobile devices such as telephones, pagers, personal digital assistants (PDA""s), data terminals etc. are designed to be carried throughout the system from cell to cell. Each mobile device is capable of communicating with the system backbone via wireless communication between the mobile device and an access point to which the mobile device is registered. As the mobile device roams from one cell to another, the mobile device will typically deregister with the access point of the previous cell and register with the access point associated with the new cell. In certain situations, the mobile device will become idle and the mobile device will enter a sleep or idle mode to conserve power. The problem is that when the mobile device is awaken by a communication from another device, it can take several minutes to reestablish a connection and a communication session between the devices. Reestablishing this communication session requires utilization of several minutes of battery power each time the main processor is awaken.
Accordingly, there is an unmet need in the art for a system and method that allows a mobile communication device to quickly reestablish a communication session, while still providing a mechanism for conserving power during idle mode.
The present invention relates to a system and method that provides a mobile communication device with the ability to quickly reestablish a communication session with another device, such as an access point or the like, after the communication device is awaken from a sleep or idle mode. The mobile communication device is provided with a first power system for powering a central processing system and a second power system for powering a radio device (e.g., a PCMCIA radio card). A mobile communication device establishes a communication session with another communication device by establishing a connection via the radio device and establishing a communication session in a stack of a central processing system. During an idle period, the communication session in the stack is stored in memory. The first power system and the central processing system will then enter a low power or sleep mode, while second power system and the radio device maintain a communication connection with the other device. Upon receiving a communications directed to the mobile communication device, the first power supply and the central processing system will wake up. The central processing system will then copy the previous communication session from the memory into the stack and reestablish the communication session with the other device. This eliminates the time necessary for reestablishing a new connection by the radio device to the other device and reestablishing a new communication session by the central processing system with the other device.
In one aspect of the invention, the device has three different modes of operation which are normal mode, enhanced mode and hot mode. A central operating system resides and runs on the central processing system. In normal mode, the system is powered up and the operating system loads the radio device driver. The radio device driver loads the configuration and configures all radio device slots. A communication session between another device can then be initiated. In a suspend state, the main processor enters a sleep mode and the communication session is terminated. If the device receives a communication for the main processor, the device enters a hot mode waking up the main processor which reloads the radio driver and reloads the configuration settings. In enhanced mode, the system is powered up and the operating system loads the radio device driver. The radio device driver loads the configuration and configures all radio device slots. A communication session between another device can then be initiated. In a suspend state, the main processor loads the communication session from the stack into memory and loads the configuration settings into the memory. The main processor then enters a sleep mode, while the radio device continues keeping the communication session or link open. If the device receives a communication for the main processor, the device enters a hot mode waking up the main processor which retrieves the communication session and configuration information from the memory. The communication session then continues uninterrupted. The device mode may be user configurable between the normal mode and the enhanced mode, for example, by providing an input selection component on an input panel or the like.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.